was locked on the outside."
"He might have gone into the corridor and locked the door after him," objected Tignol.
Coquenil shook his head. "He could have locked the door after him on the outside, not on the inside; but when we came in here, it was locked on the inside. No, sir, that door to the corridor has not been used this evening. The murderer bolted it on the inside when he entered from the alleyway and it wasn't unbolted until I unbolted it myself."
"Then how, in Heaven's name——"
"Exactly! How could a man in this room kill a man in the next room? That is the problem I have been working at for an hour. And I believe I have solved it. Listen. Between these rooms is a solid wooden partition with no door in it—no passageway of any kind. Yet the man in there is dead, we're sure of that. The pistol was here, the bullet went there—somehow. How did it go there? Think."
The detective paused and looked fixedly at the wall near the heavy sideboard. Tignol, half fascinated, stared at the same spot, and then, as a new idea took form in his brain, he blurted out: "You mean it went through the wall?"
"Is there any other way?"
The old man laid a perplexed forefinger along his illuminated nose. "But there is no hole—through the wall," he muttered.
"There is either a hole or a miracle. And between the two, I conclude that there is a hole which we haven't found yet."
"It might be back of that sideboard," ventured the other doubtfully.
But M. Paul disagreed. "No man as clever as this fellow would have moved a heavy piece covered with plates and glasses. Besides, if the sideboard had been moved, there would be marks on the floor and there are none. Now you understand why I'm interested in that Japanese print."
Tignol sprang to his feet, then checked himself with a half-ashamed smile.
"You're mocking me, you've looked behind the picture."
Coquenil shook his head solemnly. "On my honor, I have not been near the picture, I know nothing about the picture, but unless there is some flaw in my reasoning——"
"I'll give my tongue to the cats to eat!" burst out the other, "if ever I saw a man lie on a sofa and blow blue circles in the air and spin pretty theories about what is back of a picture when——"
"When what?"
"When all he had to do for proof was to reach over and—and lift the darn thing off its nail."
Coquenil smiled. "I've thought of that," he drawled, "but I like the suspense. Half the charm of life is in suspense, Papa Tignol. However, you have a practical mind, so go ahead, lift it off."
The old man did not wait for a second bidding, he stepped forward quickly and took down the picture.
"Tonnere de Dieu!" he cried. "It's true! There are two holes."
Sure enough, against the white wall stood out not one but two black holes about an inch in diameter and something less than three inches apart. Around the left hole, which was close to the sideboard, were black dots sprinkled over the painted woodwork like grains of pepper.
"Powder marks!" muttered Coquenil, examining the hole. "He fired at close range as Martinez looked into this room from the other side. Poor chap! That's how he was shot in the eye." And producing a magnifying glass, the detective made a long and careful examination of the holes while Papa Tignol watched him with unqualified disgust.
"Asses! Idiots! That's what we are," muttered the old man. "For half an hour we were in that room, Gibelin and I, and we never found those holes."
"They were covered by the sofa hangings."
"I know, we shook those hangings, we pressed against them, we did everything but look behind them. See here, did you look behind them?"
"No, but I saw something on the floor that gave me an idea."
"Ah, what was that?"
"Some yellowish dust. I picked up a little of it. There." He unfolded a paper and showed a few grains of coarse brownish powder. "You see there are only board partitions between these rooms, the boards are about an inch thick, so a sharp auger would make the holes quickly. But there would be dust and chips."
"Of course."
"Well, this is some of the dust. The woman probably threw the chips out of the window."
"The woman?"
Coquenil nodded. "She helped Martinez while he bored the holes."
Tignol listened in amazement. "You think Martinez bored those holes? The man who was murdered?"
"Undoubtedly. The spirals from the auger blade inside the holes show plainly that the boring was done from Number Six toward Number Seven. Take the glass and see for yourself."
Tignol took the glass and studied the hole. Then he turned, shaking his head. "You're a fine detective, M. Paul, but I was a carpenter for six years before I went on the force and I know more about auger holes than you do. I say you can't be sure which side of the wall this hole was bored from. You talk about spirals, but there's no sense in that. They're the same either way. You might tell by the chipping, but this is hard wood covered with thick enamel, so there's apt to be no chipping. Anyhow, there's none here. We'll see on the other side."
"All right, we'll see," consented Coquenil, and they went around into Number Six.
The old man drew back the sofa hangings and exposed two holes exactly like the others—in fact, the same holes. "You see," he went on, "the edges are clean, without a sign of chipping. There is no more reason to say that these holes were bored this side than from that."
M. Paul made no reply, but going to the sofa he knelt down by it, and using his glass, proceeded to go over its surface with infinite care.
"Turn up all the lights," he said. "That's better," and he continued his search. "Ah!" he cried presently. "You think there is no reason to say the holes were bored from this side. I'll give you a reason. Take this piece of white paper and make me prints of his boot heels." He pointed to the body. "Take the whole heel carefully, then the other one, get the nail marks, everything. That's right. Now cut out the prints. Good! Now look here. Kneel down. Take the glass. There on the yellow satin, by the tail of that silver bird. Do you see? Now compare the heel prints."
Papa Tignol knelt down as directed and examined the sofa seat, which was covered with a piece of Chinese embroidery.
"Sapristi! You're a magician!" he cried in great excitement.
"No," replied Coquenil, "it's perfectly simple. These holes in the wall are five feet above the floor. And I'm enough of a carpenter, Papa Tignol," he smiled, "to know that a man cannot work an auger at that height without standing on something. And here was the very thing for him to stand on, a sofa just in place. So, if Martinez bored these holes, he stood on this sofa to do it, and, in that case, the marks of his heels must have remained on the delicate satin. And here they are."
"Yes, here they are, nails and all," admitted Tignol admiringly. "I'm an old fool, but—but——"
"Well?"
"Tell me why Martinez did it."
Coquenil's face darkened. "Ah, that's the question. We'll know that when we talk to the woman."
The old man leaned forward eagerly: "Why do you think the woman helped him?"
"Somebody helped him or the chips would still be there, somebody held back those hangings while he worked the auger, and somebody carried the auger away."
Tignol pondered this, a moment, then, his face brightening: "Hah! I see! The sofa hangings were held back when the shot came, then they fell into place and covered the holes?"
"That's it," replied the detective absently.
"And the man in Number Seven, the murderer, lifted